Most present day medical electrode pads are of the disposable type. The typical pad includes a pad member surrounding an electrode and includes an adhesive material on its bottom surface except for a central portion which contains a conductive jelly for making good electrical contact with a patient's skin when the pad is pressed in place. A cable terminating in an electrode connector is connected to an electrode projection on the pad so that proper electrical connection is effected. Several such disposable electrode pads may be located at strategic positions on a patient and small electrical signals indicative of the function being monitored may be recorded.
After the record has been completed, the electrode connectors are removed from the electrode projections on the electrode pad. The pad is then simply removed from the patient and thrown away.
Problems currently experienced with many present day electrodes may be summarized as follows:
1. Artifacts (spurious signals) are cuased by relative movement between the electrode and the electrode connector resulting from movement of the electrical connector line extending from the electrical connector. Such movement can be a result of the relatively long lines used in some instances as well as from the movements of the patient.
2. Artifacts are also generated when the impedance between the metallic electrode and the patient's skin changes. Such impedance change is caused by an increased space between the skin and the electrode when the connector line is pulling against the electrode.
3. Patient movements often cause the breakage of connector lines due to tension.
4. Because of the freedom of movement of the connector line, there is wear on the line and frequent replacement is often necessary.
The foregoing problems have plagued the hospital industry since the inception of disposable type electrodes. As an attempted solution, large quantities of adhesive tape have been used to tape the lines to the patient. For example, if portions of the line extending from the connector could be taped to the patient it is clear that relative movements between the connector and the electrode projection itself would be substantially reduced since movements of the remaining portions of the line beyond those portions fastened to the patient would have little effect on the connecting portions to the electrode. However, utilizing conventional adhesive tape in this manner has brought along many new problems. For example, the large quantity of adhesive tape for each of the electrodes involved (and there may be 4-6 electrodes during any one recording session) obstructs other diagnostic procedures including defibrillation. Further, the adhesive tape itself is irritating to the patient and requires shaving of a large skin area if it is to be effected in adhering to the skin. This latter problem creates another problem in the increased cost and time for skin preparation. Finally, there is general discomfort to the patient when the various cables or lead wires are mass-taped to his skin.
The above problems have been solved to a substantial degree by the pad disclosed in U.S. Pat. No. 4,331,153 granted to the present applicant in 1982. The disposable electrode disclosed therein includes a pad with a cut extending inward from one side to form an auxiliary pad portion. The auxiliary pad portion is used to secure the electrode line in relation to the patient's skin and to the electrode.
While the above device has met with commercial success as a practical product for securing the electrode line in place, several difficulties have been noted through its extensive use in the field. Firstly, the cut simply extends into the pad and terminates at a closed end with no clearance being provided for passage of the electrode line nor any visual indication as to where the line should be placed. As a result, it is not unusual for the auxiliary pad portion to be distorted upon placement of the line underneath. It has also been found that the auxiliary pad will sometimes tear as the auxiliary pad portion is lifted to receive a portion of the electrode line.
Another difficulty has been discovered during clinical application of the electrode pad and auxiliary pad portion to a patient. Previously, the entire pad, including the auxiliary pad portion, were supplied on plastic carrier sheets that serves as the removable adhesive backing for both sections of the pad. The pads would be removed entirely from the carrier sheet and attached to the patient. The auxiliary pad portion would also tend to adhesively attach to the patient at the time the main pad body would be attached. It would then be required that the auxiliary pad portion be detached from the patient to lift the auxiliary pad upwardly in order to receive the electrode line. This would cause discomfort to the patient by the detachment of the adhesive surface of the auxiliary pad portion from the skin tissues and would decrease the final effective holding power of the adhesive along this portion of the pad.
Another problem occurred with the shape of the auxiliary pad portions. The auxiliary pad portions were formed along arcuate edges of the pad and the cut was similary arcuate. The resulting configuration of the auxiliary pad portion was therefore a somewhat tapered triangular configuration. The triangular configuration did not always provide sufficient adhesive area to adequately secure the electrode line in a stationary relationship to the associated electrode. This was also due in part to the reduced holding capability as indicated above when the auxiliary pad portion was pulled from the patient's skin and then reapplied after the electrical line had been positioned.